The use of borates, and especially borax, in hand and laundry soap compositions goes back many years. For example, see U.S. Pat. No. 60,890 which was granted in 1867, as well as U.S. Pat. Nos. 2,316,689, 3,020,237 and 3,886,087 which disclose preparation of soap compositions containing borax. Powdered hand soap compositions which are mixtures of a major amount of particulate borax and minor amount of milled soap are well-known to the art. Products such as BORAXO.RTM. Powdered Hand Soap have been used for many years in soap dispensers as a convenient and economical means of providing an alternative to bar soap. The soap is generally made by saponification of animal or vegetable fats or reaction of fatty acids obtained from such fats with caustic soda or caustic potash (sodium or potassium hydroxide) and then mixed with the particulate borax.
It has also been proposed that soap may be manufactured by reaction of fatty acids with sodium carbonate. See, for example, Reinish, Journal of the American Oil Chemists Society, 29, No. 11, pages 506-510 (1952). The mol ratio of fatty acid to sodium carbonate may vary from about 1:0.5 to 1:1 and such mol ratio determines the by-products obtained, either sodium bicarbonate or carbon dioxide. Several patents describe the production of soap by the addition of fatty acids to sodium carbonate. After the addition of fatty acid is completed, it has been suggested that relatively small amounts of detergent builders such as the phosphates, silicates, sodium sulfate, borates, etc. can be added to the composition. See British Pat. No. 473,220 and U.S. Pat. Nos. 2,992,992, 3,216,946 and 3,956,160. The reaction of fatty acids with caustic soda in the presence of known detergent additives has also been suggested. See British Pat. No. 376,098 and U.S. Pat. No. 2,664,399. According to U.S. Pat. No. 2,664,399, borax as well as detergent additives such as phosphates and soda ash may be present during reaction of the fatty acid with caustic soda or KOH.